Washington — When the history of the Obama presidency is written, this will be the week when President Obama put his personal prestige on the line and went for broke on his signature initiative, healthcare reform.

The president has become a combination of Candidate Obama, taking his arguments straight to the American people on a daily basis, and Back-Room Obama, twisting arms of key members of Congress in an effort to muscle through reform. Tuesday afternoon, in televised remarks from the Rose Garden, Obama struck a positive note on reform efforts.

“Make no mistake, we are closer than ever before to the reform that the American people need, and we’re going to get the job done,” Obama said.

It is a high-stakes game of beat the clock. Mr. Obama’s original deadline of getting bills through both houses of Congress before the start of August recess has morphed into, “Let’s pass reform by the end of this year,” as he put it in remarks Monday.

Already, by conceding that members of Congress will head home next month without finished legislation, Obama knows that he faces dangers inherent in member contact with voters – such as a backlash over the cost of reform and fears of what reform will mean for individuals who already have insurance.

With each passing day, the clock ticks closer to the start of campaign season for the 2010 midterms, which makes members of Congress increasingly leery of risk. By the end of the year, politics will be in full flower, and the chances for major reform diminish.

Obama also faces a second clock that’s impossible to predict: his popularity rating. As long as he remains above 50 percent in the job approval ratings of major polls, he will still have political capital to spend in Congress. But when/if he drops below that threshold, members -- even (or in some cases especially) those of his own party – will be harder to corral. His predecessor, George W. Bush, knows that lesson well.

This week’s PR blitz is unprecedented in its use of old media, new media, and old-fashioned personal contact, both by Obama himself and his surrogates.

Not only is Obama blanketing the airwaves with his face and voice – including a primetime press conference Wednesday evening at 8 p.m. Eastern – he’s also reaching out via new media. On Monday evening, he held a conference call for key bloggers. The White House is also ramping up its use of Twitter, an arena that Republicans had come to dominate in the healthcare battle.

In promoting this rapid-fire environment, Obama is trying to create a sense of momentum. In his remarks Tuesday, he stressed areas of “substantial common ground” in the current bills, such as agreement that legislation will extend coverage and protect consumers who change or lose their jobs.

Obama’s effort to muscle through health reform personally is not without precedent. The creation of Medicare in 1964 had a similarly tumultuous history. But Obama is no Lyndon Johnson, who came to the presidency having been a powerful Senate majority leader famous for his ability to charm and bully.

Still, Democratic strategists remain confident that something will pass. “There’s no question that nobody is going to get what they want,” says Peter Fenn, a Democratic communication specialist. “But I still think Obama gets a bill to sign by the end of the year.”